Due to the upgrading of living standard and increasing business activity, more and more people have chances to travel. In order to enable these persons to carry their baggage, many ideas and devices have been developed. For example, a solution is proposed to equip a case itself with wheels. However, the moving direction of such a case is difficult to be con%rolled. Also, a foldable cart with a length-adjustable handle assembly has been proposed. Such a foldable cart indeed can effectively help the travelers in carrying their baggage. However, the travelers must additionally take the foldable carts with them. Although, the foldable carts presently are constructed of light-weight materials, for example, plastic or aluminum tubes, it still is an inconvenience for the travelers to carry extra equipment. In order to obviate the disadvantages of said conventional carts, a cart is proposed to combine the case and the cart integrally. (Such a cart hereafter is referred as a "baggage cart".) Such a baggage cart has a telescopic handle assembly which has outer tubes fixedly installed onto the case and inner tubes fixedly connected to a handle and slideably retained within the outer tubes respectively. When a traveler uses such a baggage cart to transport his baggage, he grips the handle with his hand(s) to draw the inner tubes from the outer tubes and then moves the baggage cart. Since the telescopic handle assembly of the prior baggage cart is so constructed that the inner tubes can be locked only on an uppermost locking position of the outer tubes but cannot be locked on intermediate positions thereof, the length of the prior handle assembly cannot be adjusted to and fixedly locked in a desired position along the length of the outer tubes.